As an alternative to a full-blown parser, the C::Scan module does an extremely effective job of extracting information from C source code without relying on simple pattern matching. It's based on the Data::Flow module, and does some really fast, accurate scanning by (e.g.) replacing C strings and comments with white space (to avoid false matches within those constructs) and matching braces and parentheses to zero in on what's a function definition/declaration by syntactic position, not by regex matching.

It may not be as flexible as a full LALR parser, but it already exists, so you wouldn't have to create your own C grammar or retrofit an existing one to a parser. I don't think it does everything you're talking about, but it does enough that it would probably be an effective starting point.

(There's some really slick, mind-expanding Perl in both C::Scan and Data::Flow, which isn't surprising seeing as how they were originally written by Ilya Zakharevich. They're both worth looking at for the learning experience alone...)